public class java {
        public static void main(String[] args) {
            String id = "20233011021";
            int length = id.length();
            System.out.println("学号的长度是: " + length);
            char fourthChar = id.charAt(3);
            System.out.println("学号中第四个字符的值是: " + fourthChar);
            String lastTwoChars = id.substring(id.length() - 2);
            System.out.println("学号最后两位是: " + lastTwoChars);
        }
    }

